Do you think Usain bolt was this relaxed last year in Osaka when he knew it was likely he couldn’t handle Tyson Gay?
I don’t think so, he warmed up in tights then, not beach wear! 
Yea, when you know you’re going to win you’re going to be loose and relaxed.
If Asafa was going up against a bunch of guys who couldn’t break 10 s, he’d look pretty damn relaxed in the finals too.
And if Usain was going up against someone who was clearly capable of running a tenth of a second faster than he ran, he’d look similar to how Asafa looked during the 100 m.
And yea, even if Asafa runs a low time in some future race, unless he does it in the fourth race of a championship format, it won’t prove anything.